Where do coral reefs form? Do coral reefs form at
a quick or fast rate? Do coral reefs form as a
everday thing or at a special time?

Question Date: 2005-03-03

Answer 1:

You have asked a couple of great questions. And
Charles Darwin himself was one of the first people
to try to answer them!

Coral reefs form in
the warm shallow water of the tropics, all over
the world. The animals that make coral reefs, the
corals themselves, can only survive in water that
is warmer than about 70 degrees all year. Since
the ocean gets much colder than that here, corals
can't live in California. But, the water in many
other places (like Hawaii) is warm enough and it
is in these places where coral reefs
form.

Coral reefs are made up of millions
and millions of individual corals, who live in
colonies. Each individual makes a small external
skeleton of calcium carbonate, the same thing that
clam shells are made from. Each individual
skeleton is attached to all the others, and so
while each animal doesn't make much, the entire
structure can be huge. Imagine looking at a
single brick (like an individual coral) and
comparing it to a huge brick building (the coral
reef).

There are lots of different kinds of
corals that make up a coral reef, and each kind
grows at different speeds. Some grow very slowly
(less than 2 mm per year, or 1/10th of an inch),
but others can grow much faster, up to 10 cm per
year (or 4 inches). Since the reefs are made up
of all of these different kinds, the entire reef
will grow pretty slowly, usually around 1 cm per
year (a little less than 1/2 inch). It seems to
me like coral reefs form at a pretty slow rate,
but it really depends what you are comparing it
to!

The corals grow throughout the year,
but they seem to grow best when the water is warm
and clear. They probably grow best during the
summer, whenever it is summer where they are
growing. So coral reefs are continuous growing,
forming and changing. But since they grow so
slowly, it is really hard for us to watch this
process. Still, scientists estimate that some
coral reefs may have been growing continuously for
over a million years!

Answer 2:

Coral reefs are built from tiny creatures (smaller
than the size of a quarter) called polyps. These
soft-bodied polyps remove calcium carbonate from
ocean water and use it to in their hard outer
skeletons.

Polyps live in colonies and when
one dies, its skeleton remains for other polyps to
live on. Algae then deposit limestone to cement
polyp skeletons into place. This process of living
coral polyps building on top of the skeletons of
their predecessors slowly builds up the reef at a
rate of less than 5 inches per year.To start, you
need a few polyps to begin growing in the same
area; forming a colony on the same rock would be a
good start.

Warmth and light are also
necessary for a coral reef. Polyps cant survive in
water much colder than 61aF. Shallow waters are
good places for coral reefs to grow because
sunlight can penetrate to the reef, allowing the
algae and other plant life on the reef to undergo
photosynthesis. With these requirements, most
reefs are found in tropical waters. The Great
Barrier Reef in Australia is the most famous coral
reef, having taken over 600,000 years to reach its
present size. However, others are found off the
coasts of Florida, Brazil, Sri Lanka, and
Madagascar, to name just a few.

Answer 3:

Corals start their life as a free-swimming young
(planula larvae) that are carried by ocean
currents. The larvae will drift with the current
until it finds a hard bottom to attach itself.
Once the larvae attaches to the bottom it quickly
changes into a polyp.Corals secrete new
skeletal material at different rates, depending on
seasonal and yearly differences in the earth's
climate. This variation in growth results in a
banding pattern that can be seen in coral cores,
much like the bands on trees, and allows
scientists to age corals and determine their
growth rates. From these rings scientists have
found that corals grow very slowly, at a rate of
only 1 to 10 cm (.4 to 4 inches) per year, and
that some coral colonies are hundreds to thousands
of years old.

Answer 4:

Coral reefs form where there is (1) enough
sunlight, (2) warm temperatures, and (3) favorable
chemical conditions. Usually, this is on the
coasts of tropical land-masses or around eroding
tropical volcanic islands.Corals grow
continually, but the fossil record of coral growth
implies much slower growth rates over periods of
geologic time than we observe over human time. It
is likely that such growth is sporadic, slower at
times and faster at others.